The present invention generally relates to semiconductor devices and methods for producing semiconductor devices, and particularly, to a semiconductor device including projecting electrodes and a method for producing such semiconductor devices.
Recently, reductions in size, weight and cost are highly demanded for portable electronic devices. Accordingly, semiconductor devices which are used for such portable electronic devices have been greatly reduced in size, weight and cost.
Also, there is a tendency that a pitch between each of outer connection terminals of a semiconductor device is narrowed in accordance with the size reduction of the semiconductor device. For this reason, projecting electrodes such as solder bumps have been adapted as an outer terminal structure which is capable of realizing a fine pitch of the outer connection terminals.
On the other hand, it is necessary to carry out a positioning operation of a projecting electrode and a testing socket with high accuracy when a semiconductor device including such finely pitched electrodes is tested. Likewise, it is required to precisely perform a positioning operation between a projecting electrode and an electrode provided on a mounting board when the semiconductor device having the above-mentioned finely pitched electrodes is mounted.
As a structure of the semiconductor device including the projecting electrodes, a ball grid array (BGA) has often been adapted these days. In the semiconductor device having the BGA structure, a semiconductor element is mounted on a surface of a ceramic multi-layer circuit board or an organic type multi-layer circuit board and a plurality of solder bumps, which are the projecting electrodes, are formed on the other side of the board.
The above-mentioned semiconductor element and the solder bumps are electrically connected via an electrode portion, which is formed on the surface of the multi-layer circuit board and is wire-bonded or flip-chip bonded to the semiconductor element, and inner electrodes, which are formed in the multi-layer circuit board so as to connect the electrode portion and the solder bumps.
In addition, a sealing resin is provided on the surface of the circuit board so as to seal and protect the semiconductor element, wires and so on.
Now, in order to produce the above-mentioned BGA type semiconductor device, a semiconductor element is firstly mounted on the surface of a circuit board and the semiconductor element is electrically connected to an electrode portion formed on the circuit board using such a method as a wire-bonding method. Then, a sealing resin is provided so as to cover the semiconductor element mounted on the circuit board. Methods such as a mold method or a potting method may be used for the above-mentioned purpose. After the completion of the above procedure, solder bumps are formed on the back of the circuit board.
In the above procedure, in order to achieve a fine pitch of the projecting electrodes of the BGA type semiconductor device, it is necessary to carry out a positioning operation with high accuracy when testing or mounting the semiconductor device. That is, in the testing of the semiconductor device, for example, an edge of the circuit board is made to contact the inner surface of an IC socket so as to determine the positional relationship between the projecting electrodes of the semiconductor device and the IC socket.
Also, when the semiconductor device is mounted on a mounting board, a standard position which is set at a predetermined position of the mounting board and the edge of the circuit board are recognized by a pictured image and the positioning operation is carried out based on the position of the edge of the circuit board and the predetermined standard position.
However, in the above-mentioned method in which the circuit board of the semiconductor device is used as a base of the positioning operation, it is required that each of the solder bumps (projecting electrodes) be accurately formed at a predetermined position. That is, if the accuracy of the position of each of the solder bumps with respect to the circuit board is low, the position of the solder bumps with respect to the IC socket or the mounting board is shifted even if the circuit board is accurately positioned with respect to the IC socket or the mounting board.
Thus, it is necessary to form each of the solder bumps accurately at a respective predetermined position with respective to the circuit board. Using the conventional method, however, it is difficult to improve the positional accuracy of the solder bumps relative to the circuit board. One of the reasons for this is that a thermal expansion coefficient of an organic material, which is often used for forming the circuit board, is generally high. That is, since a number of heating processes are present in the manufacturing process of the semiconductor device, the size of the circuit board is affected by the heat and it is difficult to maintain its size accuracy.
Another reason for the above is related to an error generated when the solder bumps are formed. That is, since the solder has to be melted when solder bumps are formed on the circuit board, uncertain factors (which cause the error) such as surface tension and wettability are involved in the formation and they lower the accuracy.
In order to solve the above problem, it is a consideration to set a standard position based on the formation position of the solder bumps after the solder bumps are formed. However, in the conventional methods, it is difficult to set a standard position after the formation of the solder bumps since the solder bumps are formed after a semiconductor element, wires, sealing resin and so on are provided with the circuit board.